Generally, electric equipment using alternating current usually is plugged into an alternating current plug by a power plug through wires. As we know, alternating current power source generally is divided into 2 types, 110 voltage and 220 voltage. At present, the most common structure applied for power plug comprises 2 or 3 electric metal-pins (hot, neutral, and ground), wherein one end of the electric metal-pins is connected with the copper core of wires, after connecting, the back section of the electric metal-pins and a predetermined length of wire are molded or injection modeled with PVC to form an external body of the power plug, and the external body is suitable for being held by hand. The external body comprises a flexible rear fin, and enables the front section of the electric metal-pins exposed outside the power plug to contact the electric metal-sheet for conducting electricity, in this way, a power plug made of PVC is completed.
As we know, the electric metal-pin of a power plug generally is the easiest part to accumulate heat when using, especially the part between electric metal-pins and core of the wires usually is the key place for shorts and fires. If the equipment is overloaded, the temperature will increase.
Therefore, the PVC of the conventional used power plug, which contacts the electric metal-pins, will be hardened after a period time of using because of heat, resulting in the position changing between the two electric metal-pins or deforming the power plug. When in an abnormal overload condition and the temperature in electric metal-pins is increasing, if users do not shut down the power in time and check the equipment, which will melt the PVC and result in high temperature sparks. These conditions will make electric wires or equipment catch fire more easily, even resulting in fire accidents.
Then, if the conventional power plug can display a warning function when abnormal temperature increases, accidents will be avoided at an early stage.